FROM THE beginning of the Syria crisis almost three years ago, the Obama administration has found reasons to remain aloof. Every option for U.S. involvement — arming moderate rebels, enforcing a no-fly zone, carving out humanitarian corridors — entailed risks. But every imperfect option for action must be weighed against the risks of inaction: What happens if the United States fails to help shape or contain a dangerous situation? In that framework, it’s instructive to look at just one day’s news from the region:

“This is the future threat,” one expert told The Post’s Joby Warrick. “These are the children of al-Qaeda.”

● In Iraq, “suicide bombers and gunmen killed scores” as that nation tipped back “into its deadliest levels of violence in five years,” Reuters reported. Iraq’s regression has numerous causes, including the prime minister’s intransigence and President Obama’s withdrawal of all U.S. troops, but no factor looms larger than the spillover from al-Qaeda’s growing presence in Syria.

● Al-Qaeda-inspired violence also spread westward, the Wall Street Journal reported, as “Sunni extremists have stepped up attacks on the Lebanese army . . . undermining the army’s attempts to assert its authority around the country.” The United States has spent $1 billion trying to bolster that army since 2006, the Journal noted.

●As far away as Bulgaria, an influx of Syrian refugees is fueling resentment and the rise of far-right, nationalist political forces, PBS’s “NewsHour” reported.

A day’s gleaning from the U.S. press inevitably leaves out many issues: the strains imposed on Lebanon, Turkey and Jordan by hundreds of thousands of refugees; the imperilment of Syria’s Christian minority; the irreparable loss of archeological sites and centuries-old mosques and souks, and more. Still, the litany of one day is sobering enough.

It’s impossible to know what U.S. leadership could have achieved, but it’s hard to imagine a more frightful outcome. The one advantage of inaction seems to be the ability to disclaim responsibility: We didn’t break it, so we don’t own it. Even that benefit, however, may prove transient. Already the United States is the largest donor of refugee aid. As misery spreads and anti-American radicals plant roots, the Obama administration, or its successor, may find that the costs of non-involvement far exceed those that would have come with timely and measured intervention.

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